Ein Versuch zur phänomenologischen Beschreibung der Wasserstoffpermeation durch Stähle und ihre Behinderung durch Oxidfilme
Stöver, Detlev
Buchkremer, Hans Peter / Hecker, R.
Werkstoffsynthese und Herstellungsverfahren; IEK-1
Jülich Kernforschungsanlage Jülich GmbH, Zentralbiliothek, Verlag 1982
44 p.
Berichte der Kernforschungsanlage Jülich 1771
Please use the identifier: http://hdl.handle.net/2128/12296 in citations.
Experiments are presented investigating the action of corrosion scales on several steels against hydrogen and tritium permeation. We are interested in such model experiments to learn how to prevent tritium permeation from the primary circuit of an HTR to the secondary side. The same problem might be of some importance in later fusion reactor technology. Our corrosion scales were formed in a temperature range between 500° C and 950° C under varying steam hydrogen mixtures. Thickness of the scales was up to several ym. By adequate choice of the "process" parameters we succeeded to produce oxid scales with relativ high reduction factors for hydrogen permeation as compared with the permeation through the blank metal surfaces. Such scales also show a linear correlation between hydrogen pressure and permeation and an increased activation energy for permeation as compared to that of the blank metal. Our observations cast doubt on elder theories trying to explain the action of oxide films. We try here to apply a formalism presented first by Ash and Barrer to describe our findings. According to our experiments we believe that oxide scales formed under the conditions prevailing here act rather as a "dissociationbarrier" than as a "diffusionbarrier". We try here for the first time to describe the influence of the hydrogen permeation on the tritium permeation of the opposite side, (this is exactly the problem we normally encounter in the case of an HTR for process heat application). Our theoretical explanation shows on the one hand possibilities for producing very high reduction factors e.g. by producing oxide scales on both sides of a heat exchanger tube whereby tritium permeation may be reduced to acceptable levels in a HTR process heat plant, on the other side the models described here, give a sounder base to calculate tritium release in such plants and may be in later fusion reactor blanket configurations.